Enrich JSON-LD with inLanguage, isAccessibleForFree, and datePublished

[anurag629]

Context

Part of the SEO growth initiative (#18): Phase 4: Compound and technical polish.
Small, honest structured-data additions help search engines understand the pages and can improve rich-result eligibility.

What to do

• Add inLanguage: "en" and isAccessibleForFree: true to the SoftwareApplication nodes.
• Add datePublished/dateModified to the WebSite node (keep values truthful).
• Do not add ratings/reviews (no accounts, per the existing note in lib/jsonLd.ts).

Where

lib/jsonLd.ts.

Acceptance criteria

• New fields present and validate in the Rich Results Test
• npm run lint && npm run test && npm run build passes

Notes

Branch off develop (feat/*, docs/*, chore/*), open a PR into develop, and squash-merge. See CONTRIBUTING.md.